LLY: Reposting Brothers Truck Having Issues

[RobsDmax]

Reposting for my brother, any help is appreciated.

Hey Guys,

Having weird issues with my LLY and after trying an injector, feel I need to come back and ask for some help. Did my Head Gaskets earlier this year. No trouble and did studs, grade c gaskets, and otherwise just checked it all over. All good for 4 months. Now new problems.

Truck has 330,000 KMS, and is an 05 LLY ECSB. Most Modifications in Sig i think, if not just ask and I'll answer.

First about two months ago, I blew the return line on Injector 6 right off. Not sure if Race Plug could cause this? Replaced with new Injector Clip, worked good, never blew again.

Fast forward a month. Truck gets a pretty good shake at idle and has a miss, and Injector 6 Balance Rate runs around 13-14 all the time. Try some cleaner, lowers to 9-10, still rough at idle. Decided that the injector was bad and that was the reason for the excessive fuel return, rough idle, and poor balance rate. Order new Reman injector from GM, install tonight.

Fast forward to the drive home. Truck has continued rough idle. Balance rate is 8-9. Thought I'd drive home and do some more research. Half way home it now blows the Return Line off Injector 8.

Could this be Ice Pick? Still haven't tried that. Any advice is appreciated

 

[Chevy1925]

i would be testing return rates on all injectors and verifying correct rail pressure for actual vs desired.

 

[RobsDmax]

Excellent I will have him test those. I drove it this morning actual vs desired is exactly the same

 

[Yellow Jacket]

Compression check whole left bank, compare cylinder #6 to the other 3 cylinders on that side.

 

[Awenta]

Compression check whole left bank, compare cylinder #6 to the other 3 cylinders on that side.

I agree. A bent rod will do that to rates.

Cracked piston would most likely max out balance rates. (15)

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[RobsDmax]

I drove it this morning, injectors 3 and 8 were both -5 to -7, injector 6 (the one we replaced) was about +9 on the drive.

 

[Awenta]

Smoke? Blowby?

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[RobsDmax]

That is the odd thing, none of either!! It just shakes, the oil cap sits perfectly flush when checking for blowby, and no smoke from PCV or from the tail pipe.

 

[Awenta]

How's the crank pulley look while running?

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[RobsDmax]

Never thought too check it.... I will when he gets back. He took it too GM.

 

[RobsDmax]

Update, GM did a compression test on it, here is what we got.
Cyl1 340
Cyl2 420
Cyl3 340
Cyl4 390
Cyl5 350
Cyl6 420
Cyl7 360
Cyl8 390

Still shaking, going to run injector cleaner via the back of the motor and see if this helps, although we are kind of stumped.

 

[S Phinney]

Update, GM did a compression test on it, here is what we got.
Cyl1 340
Cyl2 420
Cyl3 340
Cyl4 390
Cyl5 350
Cyl6 420
Cyl7 360
Cyl8 390

Still shaking, going to run injector cleaner via the back of the motor and see if this helps, although we are kind of stumped.

With those numbers you have a mechanical problem or they didn't know how to test it.

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[Awenta]

Low compression, high balance rates. Shortened rods?

Strange that 6 was the worst and it was one of two that were right.

Where's the truck? Maybe take it somewhere else

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[RobsDmax]

Sorry I never updated this thread. It was the reluctor wheel!! Was loose truck ended up quitting while towing our gooseneck. All fixed now.:thumb: